Insulin secretion and action with increasing age - A comparison between Middle Eastern immigrants and native Swedes

AIMS: Little is known how insulin secretion and action change over time in populations of different ethnicities. We studied changes in insulin secretion and action with increasing age in Iraqi-born immigrants and native Swedes, and investigated if the changes were modified by region of origin. METHODS: Residents of Malmö, 30–75 years of age born in Iraq or Sweden, were invited to participate in this population-based, cross-sectional study. Health examination, medical history, lifestyle, sociodemographic data, and fasting blood samples were assessed. Oral glucose tolerance tests were performed and insulin secretion (disposition index, DIo) and insulin sensitivity index (ISI) calculated using the Matsuda indices. RESULTS: In total 1881 people participated; 1193 Iraqi- and 688 Swedish born. DIo decreased with increasing age in the total study population (β for the effect of age on ln DIo: (-)0.018, 95% CI (-)0.023 to (-)0.013, P < 0.001), adjusted for origin, lifestyle and anthropometric measures. DIo was generally lower in Iraqis vs. Swedes (median: 12,712.9 vs. 14,659.2, P = 0.004), but the difference disappeared when adjusted for BMI. Further, ISI declined with increasing age in both Iraqis and Swedes. ISI was generally lower among Iraqis compared to Swedes, (median: 76.9 vs. 102.3, p < .001). The difference could not be fully explained by age, sex, lifestyle, and anthropometric measures. No significant interactions were observed. CONCLUSIONS: The levels of DIo and ISI were lower among Iraqis compared to Swedes and declined with increasing age, irrespective of origin.